Cathode Ray Tube (CRT) display was the most convenient display in the world and took a very important position in the display technology. However, due to the rapid development of the optoelectronics industry, the CRT display is gradually replaced by the flat panel displays (FPDs).
The FPDs encompass a growing number of technologies making video displays much lighter and thinner than traditional television and video displays that used CRT. Generally, the FPDs comprise liquid crystal displays, plasma displays, electroluminescent displays, light emitting diode displays, vacuum fluorescent displays, field emission displays, and electrochromic displays, etc. Among the said FPD technologies, organic light-emitting diode displays exhibit characteristics of thin, light weight, self-emission, high brightness, wide viewing angle, rapid response, low power consumption, full-colorization and good flexibility, and therefore are widely deemed as the most potential technology of the next generation of the FPDs.
Based on the materials of the organic films used, the organic light emitting technologies may be mainly classified into two categories: one is small molecule-based organic light emitting system, and the other is polymer-based organic light emitting system. Since the organic light emitting devices exhibit characteristics of light emitting diode (LED), the said small molecule-based organic light emitting system is also referred to organic light-emitting diode (OLED) and the said polymer-based organic light emitting system is also referred to polymer light-emitted diode (PLED).
Typically, an EL device comprises layers of hole injection materials, hole transport materials, electron transport materials, light emitting materials, an anode and a cathode (such as indium tin oxide, i.e., ITO). However, the said materials still need further improvement. For example, the chemical and thermal stability of the said materials should be high enough to render the life of the organic EL device longer.
Since the injection layer is located between the electrode and the transport layer of an organic EL device, it should exhibit excellent electron-injection or hole-injection property. A conventional and typical hole-injection material is a copper phthalocyanine (CuPc) compound, which is an organic molecule comprising eight nitrogen atoms. The said CuPc layer is the first organic layer next to the ITO layer. Moreover, the IP value of the said CuPc layer is 5.0 eV, which is close to the IP value of ITO. Hence, the efficiency of hole-injection of the CuPc layer is pretty good. However, the CuPc film is not completely transparent and may absorb the red light, and therefore the application of the said layer in a full color display has poor performance. Additionally, since the CuPc is easily crystallized, the surface roughness of the layer may be raised when the thickness of the layer is increased, thereby increasing the production of the defects. The other suitable hole injection material is TNATA (IP=5.1 eV, Tg=110° C.), which is commonly used to replace the CuPc material. The said TNATA layer has better transparency than the CuPc layer in the visible spectrum. However, the thermal stability of the TNATA layer needs considerable improvement.
In view of the above, the present invention provides a novel amine compound exhibiting excellent hole-injection property and thermal stability. Moreover, the claimed compounds are suitable for the application in an organic EL device.